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| #include <stdio.h>
#define PI 3.1415
#define R 1
void main()
{
double r, s;
printf("输入一个半径值：");
scanf_s("%lf", &r);
#if R
s = PI * r * r;
printf("圆面积是：%lf\n", s);
#else
s = r * r;
printf("矩形面积是：%lf\n", s);
#endif
}
|